Sort sequences and normalization in SQL

A sort sequence defines how characters in a character set relate to each other when they are compared or ordered. Normalization allows you to compare strings that contain combining characters.

The sort sequence is used for all character, and UCS-2 and UTF-16 graphic comparisons performed in SQL statements. There are sort sequence tables for both single byte and double byte character data. Each single byte sort sequence table has an associated double byte sort sequence table, and vice versa. Conversion between the two tables is performed when necessary to implement a query. In addition, the CREATE INDEX statement has the sort sequence (in effect at the time the statement was run) applied to the character columns referred to in the index.

• Sort sequence used with ORDER BY and row selection
  To see how to use a sort sequence, run the examples against the STAFF table shown in this topic.
• Sort sequence and views
  Views are created with the sort sequence that was in effect when the CREATE VIEW statement was run.
• Sort sequence and the CREATE INDEX statement
  Indexes are created using the sort sequence that was in effect when the CREATE INDEX statement was run.
• Sort sequence and constraints
  Unique constraints are implemented with indexes. If the table on which a unique constraint is added was defined with a sort sequence, the index will be created with that same sort sequence.
• ICU sort sequence
  When an ICU (International Components for Unicode) sort sequence table is used, the database uses the system's ICU support (Option 39) to determine the weight of the data according to language-specific rules specified by to the locale of the table.
• Normalization
  Normalization allows you to compare strings that contain combining characters.